1. Field of the Invention
This invention relates generally to synchronization of a communications system, and, more specifically, to detecting block boundaries and synchronizing the system based on this information.
2. Related Art
In current satellite broadcast systems compliant with the DVB standard, a standard encoded MPEG frame begins with a known sync byte. This byte is inserted into the frame prior to encoding by the convolutional encoder in the transmitter, and hence is encoded along with the rest of the frame. At the receiver, a decoder decodes the frame, and the receiver synchronizes the system after detecting the presence of the known sync byte.
If the code has low coding gain, as is the case with the first iteration of an inner code in a serially concatenated turbo code, there is a serious risk that the receiver will not be able to detect the presence of the sync byte. Consequently, the receiver will not be able to function since synchronization of the system cannot be achieved.
In the Japanese Digital Satellite standard, a ‘superframe header’ contains several fields that convey system information to the receiver. This header does not perform any synchronization function. Thus, in order for this header to be interpreted, the receiver must already be synchronized and have knowledge of the location of this header. Accordingly, the acquisition process with such systems can be unduly prolonged. In addition, the header consumes system overhead, and thus adversely impacts system throughput.